1. Field of the Invention
The present invention relates to an ink jet recording apparatus for ejecting ink droplets against a recording medium, and to a recording control method and a storage medium with a recording control program stored therein.
2. Related Background Art
Ink jet recording apparatuses have been developed that eject droplets of a recording liquid from an ejection port (a discharge orifice) at the tip of a liquid passage in a nozzle for recording.
A representative example of a recording head used for such a recording apparatus uses thermal energy to generate bubbles in ink in order to eject the ink based on the generation of bubbles. All the generated thermal energy, however, is not consumed during ejection, and the residual thermal energy is accumulated and may increase the temperature to the extent that the recording head adversely affects the recording characteristics.
In general, an increase in temperature reduces the viscosity of a recording liquid (ink) to increase the amount of ink ejected beyond a predetermined value, thereby adversely affecting images or increasing the amount of ink used and thus running costs. If this increase in temperature is large, the recording head may be prevented from ejection or may be damaged.
Thus, conventional measures provide a radiating member in the apparatus or the recording head or provide the recording head with predetermined time required for cooling.
In addition, drive pulses are controlled depending on the temperature of the recording head in order to stabilize the amount of ejection despite an increase in the recording head. For example, as shown in FIGS. 4A to 4C, a double pulse is normally used for driving as shown by pulse waveform in FIG. 4A, but as the temperature of the recording head increases, a pulse width t1 is reduced as shown in FIG. 4B. Finally, a single pulse is used to control drive pulse as shown in FIG. 4C. Such drive pulse control can reduce the ejection efficiency relative to thermal energy to maintain the amount of ejection at a low level. That is, the conventional techniques stabilize the amount of ejection by changing the drive pulse from FIG. 4A to FIG. 4B and FIG. 4B to FIG. 4C as described above as the temperature of the recording head increases.
There is, however, a demand for the miniaturization or elimination of the radiating member as one of the improvements associated with the miniaturization of the recording head and cost reduction. In addition, the omission of measures such as the cooling time is also requested to achieve recording at a high speed.
On the other hand, the improvement of the drive pulse shown in FIGS. 4A to 4C enables recording until the recording head reaches 80xc2x0 C. FIG. 5 shows the relationship between the increase in the temperature of the recording head and the amount of ink ejected in the case in which the drive pulse is controlled as shown in FIGS. 4A to 4C. FIG. 5 shows that when the head temperature (the temperature of the recording head) exceeds 50xc2x0 C., the amount of ink ejected rapidly increases with increasing head temperature and that at 80xc2x0 C., this amount becomes double the value obtained at the ordinary temperature. Thus, the amount of ink ejected increase far beyond the predetermined value to adversely affect images and to increase the amount of ink used and thus running costs.
In addition, the increase in the amount of ink ejected increases the time from the start of ink ejection until an ink channel is filled with the ink, that is, delays ejection return (refilling), thereby making ejection unstable or disabling ejection and increasing mists.
Furthermore, the head temperature is expected to further increase due to the further improvement of the drive pulse.
The present invention is provided to solve these problems, and its object is to provide an ink jet recording apparatus and recording control method that precludes an excessive amount of ink from being ejected despite an excessive increase in the temperature of the recording head to prevent a further increase in temperature and to enable sufficient ejection return (refilling), thereby preventing the corresponding image from being disturbed, as well as a storage medium with a recording control program stored therein.
To achieve this object, this invention provides an ink jet recording apparatus for ejecting a recording liquid from an ejection port at the tip of a liquid passage in a nozzle, characterized by comprising a recording head temperature detection means for detecting the temperature of the recording head and an image data change means for changing print image data according to the detection output of the recording head temperature detection means.
The image data change means may provide control such that the amount of print image data thinned from print image data is increased depending on an increase in the temperature of the recording head in accordance with the output from the recording head temperature detection means.
In addition, the image data change means may thin the first of at least two continuous dots of print image data at the individual ejection port.
Moreover, the apparatus may include a recording head drive control means for controlling driving conduction pulses for the recording head according to the detection output from the recording head temperature detection means.
Moreover, the recording head drive control means may apply driving conduction pulses such that at the individual ejection port, at least the dot following the thinned print image data has a larger amount of ejection than the other dots.
Moreover, the recording head uses thermal energy to generate bubbles in a recording liquid in order to eject the liquid with the generation of bubbles.
In addition, this invention provides a recording control method for an ink jet recording apparatus for ejecting a recording liquid from an ejection port at the tip of a liquid passage in a nozzle, comprising the first step of using a temperature sensor to detect the temperature of a recording head, the second step of printing print image data after thinning the data depending on the temperature detected at the first step, and the third step of printing print image data that has not been thinned at the second step by controlling drive pulses so as to provide a sufficient amount of recording liquid ejected.
The second step may set a thinning rate such that the amount of print image data thinned from print image data is increased depending on an increase in the temperature of the recording head detected at the first step.
In addition, the second step may determine the thinning rate by referencing a predetermined table that determines the relationship between the temperature of the recording head and the thinning rate.
Moreover, the second step may thin the first of at least two continuous dots of print image data at the individual ejection port.
Moreover, the third step may control driving conduction pulses for the recording head depending on the temperature of the recording head detected at the first step.
Moreover, the third step may apply driving conduction pulses such that at the individual ejection port, at least the dot following the thinned print image data has a larger amount of ejection than the other dots.
Furthermore, this invention provides a storage medium having stored therein a control program for controlling recording executed by an ink jet recording apparatus for ejecting a recording liquid from an ejection port at the tip of a liquid passage in a nozzle, characterized in that the control program allows a computer to detect the temperature of a recording head based on the output from a temperature sensor, to print print image data after thinning the data depending on the detected temperature, and to print print image data that has not been thinned by controlling drive pulses so as to provide a sufficient amount of recording liquid ejected.
Based on the above configuration, this invention detects the temperature of the recording head and thins dots of print image data according to the detected value to prevent an excessive amount of ink from being ejected. Consequently, the generated thermal energy can be reduced to preclude a further increase in temperature.
In addition, this invention controls the drive pulses for the dots preceding and following a thinned dot of print image data to thin the data in order to preclude the corresponding image from being adversely affected, thereby stabilizing the amount of ejection.
In addition, this invention increases the amount of print image data thinned with increasing temperature of the recording head to stabilize the amount of ejection.
In addition, this invention thins the first of two continuous dots of print image data at the individual ejection port to enable refilling for the second dot without delay, thereby preventing the corresponding image from being degraded due to insufficient refilling.
In addition, this invention controls drive pulses so that at the individual ejection port, the dot following the thinned print image data has a larger amount of ejection than the other dots, thereby preventing the thinning of print image data from adversely affecting the corresponding image.